1. Field of the Invention
This invention pertains generally to assessing the impact of scholarly works (references), and more particularly to the development of a network of usage information and the application of social network metrics to the network to determine the relative impact of a scholarly work.
2. Description of Related Art
The growing body of research literature necessitates a way to organize and manage the information to make it accessible to those seeking it. Various indexes have been developed, including title indexes, title word indexes, keyword indexes, subject indexes, and, finally, citation indexes.
Citation indexes and databases were developed for researchers to find out what other researchers were interested in their work and who was using various available methodologies. Citation indexing has lead to development of various tools, which are used to rank the prestige of journals, publications, institutes, universities, and authors. The concept of journal impact Ig can be measured and represented in a number of different ways. The most prevalent index is the Institute of Scientific Information's Impact Factor (ISI IF), which has been in use for at least 40 years.
The ISI IF represents journal impact as the ratio between the number of citations to articles published in a journal over a 2 year period, divided by the total number of citeable articles published in that same period. It expresses the impact or quality of a journal in terms of the degree to which its articles are cited in the literature.
Regardless of the set of assumptions about what motivates authors to cite that underlie the ISI IF, and the issues that arise when it is being applied in a range of domains, the ISI IF as an operationalization of Ig can be characterized by three main features:
(1) It is based on a frequentist metric: journal impact is largely determined by counting the number of citations to a journal. Each citation is counted as a vote of confidence for the particular journal, and a citation count amounts essentially to a poll of experts (authors) on the impact of a journal.
(2) It is based on a selection made by the ISI of all published journals.
(3) It is determined from citation frequencies as they occur for a global, nonspecific community of authors.
First, by its focus on citation frequencies the ISI IF focuses on a highly particular aspect of Ig, thereby ignoring more contextual indications of journal impact. For example, do journals which receive citations mostly from high impact journals also have high impact in spite of a relatively low absolute citation count? Does a journal that contains a high number of out-going citations function as a “hub” in the citation graph and thereby have higher impact than the number of its in-coming citations alone would indicate? Does a journal whose articles critically connect different scientific domains have high impact? These examples pertain to structural features of impact which a frequentist metric of Ig, such as the ISI IF, does not express.
Second, the ISI IF is calculated on the basis of citation frequencies which have been registered for an ISI-defined set of selected scholarly journals. This core set of journals does not include a majority of the growing body of web-based publications, gray literature, and multimedia collections.
Finally, the ISI IF is based on the journal citation patterns of a global community of authors (an author generated network (AGN)). It thus represents a global, consensus view of journal impact. Local author and reader communities can, however, have strongly diverging views. Therefore the ISI IF, as a “global” metric of impact, cannot provide an accurate assessment of the degree to which a particular Digital Library's collection fits the needs of its local community.